BIO 320 Lecture Notes - Lecture 17: Nuclear Localization Sequence, Autocrine Signalling, Membrane Transport Protein
Document Summary
In some cases, both cells may be signaling and target cells (i. e. , reciprocal) Most animal cells both emit and receive signals. Hormones are diluted in bloodstream so must act at very low concentrations. Also autocrine signaling, especially characteristic of tumor cells. Recognition of stimulus on outside of cell (in most cases): e. g. , ligand binds a receptor on plasma membrane. Transfer of signal (information) across membrane to cytosolic side. Transmission of signal to specific downstream target proteins that trigger cellular response. Steroid hormones (and vitamin d, etc. ) bind and activate specific nuclear receptors that function as transcription factors (for specific target genes) In most cases, inactive nuclear receptors reside in the cytoplasm to start with. The human genome encodes 48 nuclear receptors (don"t memorize), many with unknown ligands. If inactive receptor is in the cytoplasm to start with, changes in conformation caused by ligand binding shown here also leads to its nuclear import (e. g. , by exposing a nuclear localization sequence.
